This invention relates to sensors, as well as controllers and sensor systems including such sensors and controllers.
For effecting controls of different kinds, say, in an FA system, it has been known to connect sensors to a PLC, to transmit control commands to a target apparatus intended to be controlled by the PLC and to thereby effect controls such as coordination and synchronization. More recently, sensors with signal processing functions are being developed. Such a sensor is connected downstream to a controller through a device net and this controller is connected to the target apparatus through a network such as Ethernet such that control commands are given to the target apparatus through the network on the basis of information from the sensor.
When an application program of a controller thus structured accesses sensor data or a set parameter, it is necessary for the application program to recognize the physical address (such as the address of a data port) of the sensor. A driver for making such an access, however, must be set according to the access model routine, the register model of the sensor and the contents of the functions. As multi-functional sensors are developed, it becomes necessary as a practical matter to provide a driver intrinsic to each sensor. Thus, the common practice has been to provide and incorporate drivers (intrinsic device information) in the application program for each of the sensors connected.
There are countless combinations of sensors and controllers, however, and it is difficult to preliminarily incorporate drivers for all sensors in a controller. When an external device is connected to a personal computer and a driver for this external device is required, on the other hand, it is possible to attach a recording medium such as an FD storing such a driver and install this FD in the personal computer. Since most controllers which are connected to a PLC or a sensor of another kind through a network, are not provided with a driving device for reading from a recording medium, they cannot be directly made use of.
It may also be attempted to connect onto the network a host computer with a driver device capable of reading from a recording medium, to temporarily store the driver intrinsic to the sensor through a recording medium storing the aforementioned driver on the host computer and to download this driver to the controller through the network. It is very cumbersome, however, to go through these steps every time a sensor is replaced. Since the sensor, the controller and the host are often set mutually far apart, furthermore, it makes it even more troublesome to move to each of the localities to carry out these required steps.